As in the title, the heart symbol is pretty much universally understood to mean love/caring. How long has it been this way? Why was the heart the symbol that took the meaning of love?
There is always more to be said on the topic, but while waiting for new answers to be written, you might be interested in reading u/TheYottleInTheBottle's answer in How did the ♥, come to be identified with love, and represent a heart?